1. Field of the Invention
The present invention relates to an electric-connection testing device used in electric tests on flat objects, such as integrated circuit boards and display boards.
2. Description of the Related Art
Electric tests on flat objects, such as semiconductor integrated circuit boards and display boards, are generally performed with an electric-connection testing device, such as a probe card. In an electric test, a plurality of electrodes of an object to be tested (hereinafter, may simply be referred to as an “object”) are pressed with many contacts arranged in an electric-connection testing device and are energized under such a state. Examples of the electric-connection testing device of this type include a device in which an insulating solid body or a film substrate provided with many projecting electrodes (referred to as a “contact group” here) integrally formed with traces, which are connected to the respective electrodes, is mounted on an insulating base (see, for example, Japanese Unexamined Patent Application Publication No. 2002-311049).
FIGS. 8 and 9 show a known technology represented by an example disclosed in Japanese Unexamined Patent Application Publication No. 2002-311049 (a cross-shaped leaf-spring structure is integrated with a pyramid rigid block). In a contact unit to be pressed against electrodes of an object, a projecting contact group 1 and a substrate 2 provided with wiring of the contact group 1 are secured to a rigid body 4, which is bonded to a base 3 with a cross-shaped leaf spring 5 interposed between the rigid body 4 and the base 3. When the contact group 1 is pressed against the electrodes of the object, elastic deformation of the leaf spring 5 occurs as shown in FIGS. 10A to 10C and generates a pressing pressure of contacts (FIG. 10A) while compensating for a tilt error between the substrate 2 and the object (FIGS. 10B and 10C).
However, in the cross-shaped leaf-spring structure of a known electric-connection testing device described above, a translational degree of freedom (Z direction) related to the generation of a pressing pressure and two oscillation degrees of freedom (θ direction and φ direction) related to the compensation for a relative tilt error between the contact unit and the object are provided by elastic deformations of the same component. Therefore, the application of a pressure required for the contact group to ensure a good electric contact causes an excessive stress on a tilt-correction degree of freedom. This results in a nonuniform application of a pressing force from the contact group to the electrodes of the object, and an accurate electric test cannot be performed.
Theoretically, the cross-shaped leaf-spring structure described above can be replaced with a complex mechanical structure, such as a combination of a plurality of adjusting screws and a plurality of spiral springs having respective degrees of freedom, to achieve uniformity of the pressing force described above. However, the practical application of such a mechanical structure on a commercial scale is extremely difficult due to difficulties in ensuring precision and adjustment in assembly.